When reading about the complex world of watches, you’re bound to come across some very specific terminology. While some of them are self-explanatory, others require a little more knowledge to understand. To help you decipher these terms, here is a comprehensive glossary of common terms and names used when referring to watches, horology, and timekeeping.

A

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Alarm

A mechanism that makes a sound at a pre-determined time.

Altimeter

An instrument that measures altitude

AM/PM Indicator

An indicator a 12-hour display that shows whether it’s nighttime or daytime. Also referred to as a Day/Night Indicator.

Analog Watch

A watch that indicates the time via hands on a dial.

Aperture

A small window on a dial. Typically refers to a calendar window to show the date, day, month, or moonphase.

Annual Calendar

A watch that indicates the time, day, date, month, and leap year (often moon phase too) correctly throughout the year with only the need for one manual adjustment at the end of February.

Anti-Magnetic

A watch built to withstand the detrimental effects of magnetic fields.

ATM

Unit used to measure atmospheric pressure. Used in watches to denote water resistance where 1 ATM equals 10 meters or 1 bar.

Automatic Movement

A type of mechanical watch movement that relies on the motion of a wrist (or watch winder) to move the rotor back and forth to automatically wind the mainspring, which then transmits energy to power the watch. If left motionless, an automatic movement will stop working until it’s wound up again. Also referred to as a self-winding movement.

Automatic Watch

A watch powered by an automatic mechanical movement.

B

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Balance Spring

A tiny spring that returns the balance wheel back to its neutral position. Also referred to as a hairspring.

Balance Wheel

The timekeeping device in a movement that swings back and forth and divides the time into equal parts. Combined, the balance spring and the balance wheel serve as the regulating mechanism of the movement much like a pendulum in a clock.

Band

A strap, typically leather, textile, or rubber, that secures the watch to a wrist.

Barrel

A round box that houses the mainspring in a mechanical movement. The exterior of the barrel has a ring of gear teeth that drives the gear train. The larger the barrel the more power reserve a movement has.

Baselworld

The largest annual watch fair that takes place in Basel, Switzerland, during the springtime. It’s when most watch brands release their novelties for the year.

Beats Per Hour (bph)

The number of vibrations/ticks/beats per hour of a watch. High-end watches boast quicker frequency rates such as 21,600 bph (6t ticks/second), 28,800 bph (8 ticks/second), or 36,000 bph (10 ticks/second). The faster the ticking the higher the precision.

Bezel

The ring that sits on top of the case to secure the crystal above the dial. There are several types of bezels including decorative ones and functional ones to track elapsed time. A bidirectional rotating bezel turns clockwise or anticlockwise. A unidirectional rotating bezel, typically used on diving watches, turns only anticlockwise.

Bracelet

A metal strap, typically steel, gold, platinum, or titanium that secures the watch to a wrist.

Bridge

Bridges are a series of plates or bars that hold components of the watch movement together and are attached to the mainplate with screws.

C

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Cabochon

A polished but not faceted stone, typically mounted onto a winding crown for decorative effect, a signature detail on many Cartier timepieces

Calendar

A watch function that indicates the date, day, month, and/or year.

Caliber

Another name for a watch movement—the mechanism that powers the watch.

Case

The main portion of the watch that houses the movement. Available in a range of metals and shapes.

Caseback

The opposite side of the dial on a watch—the portion that lies on the skin when the watch is worn. Casebacks can be snap in, screw in or screw down. Plus, casebacks can also be solid, which is typically engraved with watchmaker hallmarks, or transparent for a view of the movement within.

Chronograph

A chronograph is a watch function that can measure periods of time via a start, stop, and reset mechanism—essentially a stopwatch. Modern chronograph watches typically measure time via the central seconds hand and often come with extra subsidiary registers that can record elapsed times (in minutes and/or hours). Chronographs are quickly identified by extra pushers on the case.

Chronometer

A highly precise watch that comes with an official certification. Swiss made chronometers are certified by Controle Officiel Suisse des Chronometres (COSC).

Cloisonne

Decorative work where materials such as enamel, glass, or gems are separated by thin strips of metal. Typically found on the ornate dials of very high-end watches.

Column Wheel

Some chronographs have column wheels, which, thanks to its ratchet teeth, acts as the on/off switch for the chronograph function.

Complication

In watch speak, any additional function over and above time indication is a complication. For instance, calendar, chronograph, moon phase, minute repeater, and world timers are all complications.

COSC

Controle Officiel Suisse des Chronometres, the institute responsible for testing and certifying the precision and accuracy of Swiss watches.

Côtes de Genève

Also known as the Geneva Stripes, the Côtes de Genève is a special type of stripe-based decoration found on watch movements.

Crown

A button positioned on the outside of the case to wind the movement, set the time, and set other functions on the watch such as the date. Sometimes referred to as the winding stem. A screw-down crown improves water resistance.

Crystal

The component covering the dial, typically fashioned from acrylic, glass, or sapphire. Today, sapphire crystals are ubiquitous on luxury watches, prized for their resistance to scratching and shattering.

D

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Day-Date

A watch function that indicates the day of the week along with the date of the month like on the Rolex Day-Date

Day/Night Indicator

An indicator a 12-hour display that shows whether it’s nighttime or daytime. Also referred to as an AM/PM Indicator.

Deployant Clasp

A type of folding metal buckle on watch bands and bracelets that offers more security than a typical tang buckle. Often erroneously called a deployment clasp.

Depth Alarm

A mechanism that emits a sound when a diver submerges below a pre-set depth.

Dial

The face of the watch that houses the watch hands, indexes, and/or functions. They range in materials, colors, and decorations.

Digital Watch

A watch that displays the time using digits on a screen, typically LCD.

Dual Time

A watch that includes two hour hands to indicate the time in two different time zones. The secondary hand is typically referred to as a GMT-hand, 24-hour hand, or UTC hand.

E

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Ebauche

Unassembled movement kits that are built, modified and branded by different watch companies. The most Swiss famous ébauche movement maker is ETA and these ETA movements are the basis for many luxury watch movements.

Enamel

An opaque glassy substance applied to metal surfaces, typically used as a decorative element on dials of high-end watches.

Engine Turned

Repetitive patterns engraved into metal surfaces as a decorative technique. Also known as Guilloche.

Equation of Time

A watch complication that displays the disparity between mean solar time and true (apparent) solar time.

Escape Wheel

Part of the escapement, the escape wheel gears includes very large teeth to interact with the pallet fork, allowing the watch's wheels to advance by a fixed amount, moving the hands forward.

Escapement

Sitting between the train and the regulating organ, the escapement maintains the oscillations of the regulating organ.

F

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Flyback Chronograph

The timing on a fly-back chronograph can be reset without first having to be stopped.

Frequency

The number of vibrations or beats per hour determined in hertz (Hz) such as 4Hz (28,800 bhp) or 5Hz (36,000 bph).

G

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Gasket

Rubber rings that create airtight seals around the caseback, crystal, and crown for improved water resistance. Gaskets typically require replacing every couple of years.

Gear Train

A mechanical system comprised of mounted gears that transfers energy from the mainspring to the escapement.

Grand Prix d'Horlogerie de Genève (GPHG)

Created in 2001, the GPHG is an annual awards ceremony in Geneva, Switzerland, that awards the best watches of the year across several categories. The top prize is the “Aiguille d'Or” awarded to the very best watch of the year.

Grande Sonnerie

A complication that combines quarter striking and minute repeater complications. At every quarter hour, it sounds the hours and quarters on two gongs. It can also strike the hours on demand via a button.

Greenwich Mean Time (GMT)

Previously used as the international civil time standard, replaced by Coordinated Universal Time (UTC). Dual Time watches are sometimes referred to as GMT watches.

H

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Hack Feature

A mechanism that stops the watch completely when the crown is pulled out for precise time setting or synchronization.

Hand

The indicator that rotates around the dial to point to the hour, minute, second or any other display. Hands come in a range of shapes and sizes.

Haute Horlogerie

A French word that translates to high watchmaking to denote the very best in mechanical watches and very complex watch complications.

Helium Escape Valve (HEV)

Diving watches built to dive to extreme depths are typically fitted with Helium Escape Valves to releases gases that build up in decompression chambers. This release prevents the crystal from popping off in pressurized chambers.

Horology

The science of measuring time or the art of making instruments such as watches for indicating time.

Hour Markers

The indexes around the dial that indicate the hours. There’s a wide range of hour marker styles including sticks, batons, round plots, Arabic numerals, and Roman numerals.

I

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Integrated Bracelet

A style of bracelet that is incorporated into the watch case that became very popular in the 1970s like the Audemars Piguet Royal Oak and the Patek Philippe Nautilus

J

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Jewels

In watch movements, jewels refer to synthetic rubies used as bearings in gears to reduce friction. They are set into the drilled holes of plates and bridges.

Jump Hour

As its name suggests, the Jump Hour hand jumps to the next hour every 60 minutes rather than slowly edging towards it over the course of an hour. Sometimes, rather than a hand, a Jump Hour watch will include a window with numerals that jump to the next hour every 60 minutes.

K

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Karat

The measure of the purity of gold where 24-karats is pure gold. While many vintage watches were made in 14k gold today, gold luxury watches are almost exclusively made from 18k gold.

Keyless Works

Gears that not only wind the mainspring via the turning of the winding crown but also allow the hands to be set when the crown is pulled out. Named so because prior to this invention, keys had to be used to wind the movement.

L

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Lacquer

A hard protective coating for a range of materials. Originally made from the sap of a lacquer tree there are also synthetic substitutes today. Sometimes found as a decorative technique on the dials of high-end watches.

Lever Escapement

A type of escapement that includes a forked lever that positioned between the escape wheel and the balance that locks and unlocks the escape wheel teeth.

Liquid Crystal Display (LCD)

Composed of liquid encased between two clear plates and activated by electronic impulses, LCD is typically found on digital watches to display the time using digits.

Lugs

The protrusions on a watch case that holds a spring bar. The spring bar is what attaches the watch band, strap, or bracelet to the case.

Luminescence

A substance applied to the face a watch to emit a glow in low light. Also known as watch lume, a range of materials have been used from (highly radioactive) radium to (lesser radioactive) tritium to (nonradioactive) photoluminescence.

M

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Mainspring

The spring that is wound to supply power to the watch.

Manual-Winding Movement

A mechanical movement that requires manual winding of the crown to wind up the mainspring to power the watch. Also known as a hand-wound movement.

A chronometer specifically built for the use on a ship that can calculate longitude while sailing.

Mechanical Watch

A traditional type of watch that doesn’t require electricity to operate but rather gets its power from a wound mainspring. The two main types of mechanical watches are automatic and manual.

Minute Repeater

A watch complication that sounds the time on demand using bells or gongs.

Moon Phase Display

A watch complication that indicates the phases of the moon on the dial.

Mother-Of-Pearl

Also known as nacre, mother-of-pearl is the outer layer of a pearl or the inner layer of a shell that is sometimes used on the dials of watches—typically ladies’ luxury watches.

Movement

The whole mechanism that powers the watch. There are quartz movements powered by batteries and mechanical movements powered by a wound-up mainspring. Mechanical movements are then further divided into automatic and manual movements.

O

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Oscillation

Also known as swing, oscillation is the movement back and forth at a regular speed. For instance, each oscillation of a pendulum represents one second.

P

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Perpetual Calendar

A watch that correctly indicates the time, day, date, month, and leap year (often moon phase too) in perpetuity (forever) without the need for adjustment. The only time a perpetual calendar will need manual adjusting is in 2100 when the leap year will be ignored.

Physical Vapor Deposition (PVD)

A thin coating applied to a watch to add color. Black PVD watches are especially popular.

Power Reserve

The amount of energy that can be stored in a watch before the mainspring needs to be wound again. A power reserve indicator is sometimes placed on a dial of a watch.

Pusher

A button on a case that is pressed to drive a mechanism, for example, chronograph pushers, alarm pushers, and striking pushers.

Q

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Quartz Movement

A movement powered by a quartz crystal, which oscillates to regulate timekeeping. A quartz movement does not require winding, but rather typically gets its power from a battery. Sometimes, the battery can be recharged via solar power or kinetic energy.

Quartz Watch

A watch powered by a quartz movement.

Quick-Set

Also known as quick-date, the quick-set function allows the date to be set independently from the center hands.

R

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Rattrapante

Also known as a split-seconds chronograph, a rattrapante features two sweep seconds hand rather than just one to allow for the timing of two different events with the same start time.

Retrograde

A retrograde feature includes a hand that moves over a portion of an arc then jumps back to the beginning again rather than in a full circular motion. A retrograde display can vary to indicate the day, date, hours, minutes, and/or seconds.

Rotor

The part of an automatic movement that swings back and forth thanks to the natural motion of the wrist to wind up the mainspring.

S

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Salon International de la Haute Horlogerie (S.I.H.H.)

An important watch fair that takes place in Geneva, Switzerland at the beginning of each year. Led by the Richemont Group but increasingly including other brands, SIHH also presents watch novelties for the year.

Skeleton Watch

Also known as openworked, a skeleton watch reveals the interior of the watch as much as possible by stripping away as much of the dial, case, and movement as possible. Typically sports a transparent caseback too.

Slide Rule

Typically found on pilot watches, a slide rule bezel allows the wearer to perform a host of calculations including fuel consumption, airspeed, and distance calculations.

Small Seconds Indicator

Rather than the sweep seconds-hand on the center of the dial, a small seconds indicator displays the running seconds elsewhere on the dial, typically in a subsidiary dial.

Subsidiary Dial

Also known as a subdial or register, subsidiary dials are smaller dials placed on the main dial to indicate a range of information such as seconds, calendar, chronograph, or a secondary time zone.

Sun/Moon Indicator

A complication that displays the phases of the sun and moon over the course of the day and night.

Sweep Seconds Hand

The seconds hand positioned at the center of the dial instead of a subdial. Also typically refers to the motion of the seconds hand of a mechanical watch that “sweeps” around the dial rather than the seconds hands “ticking” around the dial on a quartz watch.

T

A telemeter is a scale on a watch dial or bezel used to determine distance based on time.

Tourbillon

A watch device invented to offset the detrimental effects of gravity by constantly rotating the balance wheel, balance spring and escapement typically within a cage. A tourbillon usually makes one full rotation every minute and is often prominently displayed on the dial.

V

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Vibrations

The movement of an oscillating component of the watch, typically five (18,000 vibrations per hour) or six vibrations per second (21,600 vibrations per hour) but can reach much higher frequencies. Also denoted by beats per hour or frequency measured in hertz (Hz).

W

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Water Resistance

The rate at which a watch can withstand exposure to water typically indicated by meters, feet, ATM or bars. Important to note that waterproof is an illegal and erroneous term in watchmaking as no watch is 100% waterproof.

Wheels

While wheels and pinions are sometimes used interchangeably, large gears made of brass are referred to as wheels and small gears made of steel are referred to as pinions. These components make up the gear train, which transfers energy from the mainspring to the escapement.

Winding

The action of winding the mainspring to power a mechanical watch. This can be done manually via the crown or automatically via a rotor that swings back and forth with the natural motion of a wrist.

World Timer

A watch complication that permits the simultaneous indication of 24 time zones around the periphery of the dial typically denoted by major cities.